The principle behind a novel form of spacecraft propulsion could be tested at the world's most powerful particle accelerator.

In 1924, the influential German mathematician David Hilbert published a paper called "The Foundations of Physics" in which he outlined an extraordinary side effect of Einstein's theory of relativity.

Hilbert was studying the interaction between a relativistic particle moving towards or away from a stationary mass. His conclusion was that if the relativistic particle had a velocity greater than about half the speed of light, a stationary mass should repel it. At least, that's how it would appear to a distant inertial observer.

That's an interesting result and one that has been more or less forgotten, says Franklin Felber an independent physicist based in the US (Hilbert's paper was written in German).....More

This is indeed very interesting, but I somehow seem to fail at understanding how this could be used for any useful kind of propulsion?

Just imagine a "Spaceship" with a big heavy particle accelerator on it, that shoots out protons. And then you would get a tiny additional "push" on top of the normal impulse from the very fast protons...